Location, Location. Two of Porsche's finest: one mid-engined, one rear-engined. Which handles better?

This is where we venture beyond customary performance tests to decipher two of car enthusiasm’s enduring mysteries: Does spotting the engine in the optimum location—in the middle of the car—yield demonstrably better handling? And can engineering theory trounce painstaking practice?

Porsche’s 2012 Cayman R, the hottest mid-engined model in Porsche’s current lineup, represents the theory side of the equation. This is the thinking man’s sports car—light, stripped, and hunkered down for utmost agility. Aluminum door skins, a bare-bones interior, carbon-fiber seat structures, and new 19-inch wheels hold the curb weight to 3076 pounds. Air conditioning and audio-entertainment equipment are optional. Porsche’s 3.4-liter, direct-injection flat-six has been goaded to 330 horsepower at 7400 rpm, a 10-hp gain over the standard Cayman S. While price doesn’t count in this analysis, the Cayman R starts at $67,250, a pocket-warming $12,700 less than a base 911.

We tapped a 911 GT3—the proud son in an unbroken line of rear-engined Porsches dating back to 1948—to represent the practice-makes-perfect argument. What the GT3 lacks in value (as-tested price: $130,910), it overcomes with pure grit. In terms of power-to-weight ratio, this is the second-hottest naturally aspirated Porsche money can buy (after the GT3 RS). The 435-hp, 3.8-liter flat-six and the six-speed transaxle powering this 911 descend from battle-hardened race hardware. Prepped GT3s compete in the Porsche Supercup, a Formula 1 support series. Decades of exorcising handling gremlins that come with hanging a 570-pound engine behind the rear axle have paid off in razor-edged reflexes. The latest fix is a $1300 set of dynamic engine mounts that cinch up during aggressive maneuvers to calm the GT3’s transient behavior.

These road warriors are the ultimate examples of their respective 987/997 breeds. A seventh-generation 911, which will beget a new, third-generation Boxster/Cayman, is scheduled to bow at this fall’s Frankfurt auto show. To compile the evidence that would convincingly prove which engine location works better, we dug deeply into our box of tools.

Cayman Dynamics, a team of vehicle-dynamics experts on call to support our more ambitious tests, cracked the door to a local laboratory where a million-dollar test rig measured each Porsche’s center-of-gravity height and polar moment of inertia [see “Engine-Location Glossary”].

Supplementing the normal acceleration, braking, and cornering tests, we lapped the Chrysler Proving Grounds road circuit where the Dodge Viper’s fangs were sharpened. All our tests were run with stability control disabled.

To measure agility and predictability at the ragged edge of adhesion, we reconfigured the classic slalom test and cooked up a new step-steering-input maneuver.

To monitor yaw rate and slip angle throughout our tests, we used a dual-antenna Racelogic VBOX II SXSL3 data logger.

And, in celebration of Michigan’s endearing spring weather, we attacked a favorite local road with each Porsche to determine which was capable of posting the higher average speed on a 1.0-mile wet-pavement run.

Clamped securely to a swinging platform, the Cayman R is ready to ride the inertia-measurement machine./b>

LET THE GAMES BEGIN

Theory says that for optimal performance, a sports car’s center of gravity (CG) should be as low as possible and closer to the drive wheels than the steering wheels. (Front-drivers read from a different chapter in the physics book.) To visualize polar moment of inertia, think of a figure skater spinning in a pirouette or a high diver tucking in limbs to accelerate rotation off the board. Now transfer those visions to a sports car: Concentrating the engine as close as possible to the vertical axis of rotation reduces the polar moment of inertia, theoretically making it easier to begin and end any cornering maneuver.

Our lab tests revealed that the GT3’s CG height is a worthwhile 0.6 inch lower than the Cayman’s. But that four-percent advantage pales in comparison to the Cayman’s 20-percent-smaller moment of inertia. Those figures tell you little on their own. But when we dig into the battery of dynamic tests, knowing the two Porsches’ inner secrets might help illuminate how one is able to trump the other.

Even though the crux of this story is handling, it’s worth noting that the 911’s acceleration and braking superiority goes beyond its better power-to-weight ratio and its track-worthy tires. Accurately knowing the CG location in both cars reveals that the rear (driving) tires carry 74 percent of the 911’s weight during hard initial acceleration versus only 67 percent of the Cayman’s. (More load equals better launch traction.) During braking, when nearly equivalent tire loading yields the shortest stops, the dynamic distribution is 58/42 percent, front to rear in the 911, versus 64/36 in the Cayman. Factor in the downforce provided by the 911’s rear wing, and the braking advantage swings further in its favor.

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*AccuPayment estimates payments under various scenarios for budgeting and informational purposes only. AccuPayment does not state credit or lease terms that are available from a creditor or lessor, and AccuPayment is not an offer or promotion of a credit or lease transaction.